The Risk Factors project has studied the very large HIV epidemic among injecting drug users (IDUs) in New York City from 1978 (using stored sera) and the very large HIV epidemic among non-injecting heroin and cocaine drug users (NIDUs) since 1995. In our current research, we have demonstrated a dramatic reduction in HIV transmission among IDUs, but also a substantial increase in HIV among NIDUS. (HIV prevalence has doubled among NIDUs in NYC over the last decade). Herpes simplex virus-2 (HSV-2) is strongly associated with HIV transmission, and we have identified prevalence HSV-2 as a major factor associated with HIV transmission among NIDUs in NYC. The specific aims of the proposed research include: 1) Monitoring risk behavior, HIV prevalence and incidence and service utilization in the continuing evolution of the HIV epidemic among NIDUs and IDUs in New York City. 2) Quantifying the long-term population-level relationships between HIV and HSV-2 infections among heroin and cocaine users in NYC, including testing the hypothesis that the strength of the association between HSV-2 and HIV increases over time. Recent intervention studies have dramatically increased the need for understanding HSV-2/HIV relationships. 3) Evaluating effects of the New York City Department of Health (NYC DOH) Condom Social Marketing campaign on sexual risk behaviors and HIV and HSV-2 infection among IDUs and NIDUs in NYC. 4) Monitoring patterns of sexual and injection related HIV transmission among IDUs in NYC. There are many linkages between NIDUs and IDUs in NYC. NIDUs and IDUs are best viewed as linked groups within a single population of heroin and cocaine users in NYC. A thorough understanding of sexual transmission among NIDUs requires an understanding of both injecting and sexual transmission among IDUs in the city. 5) Assess new patterns of racial/ethnic differences in HIV infection among NIDUs and IDUs. 6) Intervention development. These aims will be accomplished through continuation of our studies of NIDUs and IDUs entering Beth Israel drug treatment programs in NYC. The proposed research will be the first study of the spread of HIV over time in a very large population of NIDUs, the first assessment of change in the relationship of HVS-2 to HIV over time among NIDUs, and the first assessment of the effects of a very large condom social marketing campaign on sexual risk behavior of NIDUs and IDUs.